The objectives of this project are to develop a feasible approach to screening for colorectal cancer by fecal occult blood testing at home. This would select a small group for further aggressive diagnostic studies. Our goals are to evaluate patient compliance; rate of positive screening tests; true-positivity and false-positivity of screening tests for neoplasia; false-negativity, sensitivity, and specificity for diagnostic tests; pathology and staging of neoplastic lesions; survival; and cost analysis. Approximately 20,000 patient examinations have been performed. A final computer analysis has now been made of the first examination cycle which represents the first screening of the study group. The first rescreening has been completed and we are now in the phase of the second rescreening of the patient population. Prevalence of cancer was higher in the study asymptomatic patients as compared to the control asymptomatic patients. Incidence data will result from current analysis of the first rescreening. Compliance studies have been initiated and are continuing. Evaluation of the yield of diagnostic techniques indicates that colonoscopy is the single most productive test. Evaluation of the Hemoccult II slide is currently being made. A higher rate of positive slides (4-5%) for the Hemoccult II slide is being observed as compared to the rate of positivity for the original Hemoccult slide (1%). The rate of false-positives is currently being evaluated. The influence of rehydration has been studied in the laboratory and is currently being evaluated clinically. This appears to enhance the color reaction and may influence the rate of positivity. An approach to cost analysis is currently being developed.